1. Field of the Invention
The present invention relates to a semiconductor manufacturing method, a substrate processing method, and a semiconductor manufacturing apparatus, and more particularly to a semiconductor manufacturing method, a substrate processing method, and a semiconductor manufacturing apparatus with which the effect of substrate contamination caused by impurities is minimized by adjusting the environment conditions in the transfer of the substrate from the preliminary chamber to the process chamber via the transfer chamber, or from the process chamber to the preliminary chamber.
2. Description of the Related Art
In addition to the problem of floating particulate (primarily mechanical contamination) that was restricted in the past, the problem of chemical contamination caused by gaseous particles has become more pronounced in recent years as semiconductor devices have become smaller and more highly integrated. The term xe2x80x9cmechanical contaminationxe2x80x9d as used here refers to the generation of dust from mechanical moving parts such as a transfer robot, while xe2x80x9cchemical contaminationxe2x80x9d (trace chemical components) refers to contamination caused by trace amounts of volatile impurity (out-gas) components coming from chamber structures (such as the shaft seals of a transfer robot or the O-rings used as chamber seals) or the reverse diffusion of oil from a vacuum pump.
One reason contamination has become such a problem is that in the HSG (Hemi-Spherical Grained silicon) formation technique discussed in Japanese Laid-Open Patent Application H5-304273 (U.S. Pat. No. 2,508,948), for example, contamination by gaseous particles results in inconsistent bonding density in the silicon molecules, which has an adverse effect on the quality of the finished product. In an epitaxial growth technique, the presence of chemical contaminants (impurity molecules) causes mismatching in the crystallinity of the silicon (the silicon in the portions where the contaminants are present grows irrespective of the crystallinity of the silicon substrate), resulting in crystal defects or polycrystallization, and this too has an adverse effect on the quality of the finished product. Also, in a process in which a thin film is formed by gate oxide film formation or the like, one molecule of contaminant accounts for a greater proportion of the total film thickness, so the effect on film thickness uniformity and the electrical characteristics of the device cannot be ignored.
In light of the above, a cleaner environment, in which not only mechanical contamination but also chemical contamination is removed, has been required in the manufacture of semiconductor devices in recent years, and should be provided in clean rooms and to manufacturing apparatus.
With a conventional semiconductor manufacturing apparatus comprising a load-lock chamber from and to which a substrate is exchanged with the outside, a process chamber in which the substrate is subjected to a predetermined processing such as thin film formation, and a transfer chamber in which the substrate is transferred between the load-lock chamber and the process chamber, when a wafer (substrate) is transferred from the load-lock chamber to the process chamber by a transfer robot inside the transfer chamber, the pressure inside the chambers is set under the vacuum that can be attained by vacuum pump exhaust, and this pressure is maintained at 0.1 Pa or less.
However, it is possible that a chamber kept in a vacuum state under the attainable vacuum may be contaminated by trace amounts of volatile impurity components from chamber structures (such as the shaft seals of a transfer robot or the O-rings used as chamber seals) or the reverse diffusion of oil from the vacuum pump, and there was the potential for this to have an adverse effect on the wafer during its transfer.
In view of this, the following methods have been attempted to prevent such chamber contamination.
(1) Lowering the impurity partial pressure in all of the chambers by installing a turbo molecular pump or other such pump capable of producing a super-high vacuum (10xe2x88x926 Pa) in all of the chambers.
(2) Designing the transfer robot inside the transfer chamber so that a super-high vacuum can be attained.
(3) Using metal O-rings for the chamber seals.
The downside to these methods, however, was their high cost, difficulty of maintenance, and so forth.
In Japanese Laid-Open Patent Application H6-104178 (hereinafter referred to as known example) is proposed a method in which a substrate is vacuum treated using a plurality of vacuum process chambers, a transfer chamber with a built-in transfer robot for transferring the substrate, and an entry chamber and exit chamber for bringing the substrate in and out, wherein the transfer chamber is evacuated to vacuum, after which an inert gas such as nitrogen gas is continuously introduced into the transfer chamber during the operation of the apparatus, or the gas used in the vacuum processing is continuously introduced into the vacuum process chamber during the operation of the apparatus. This mainly prevents contamination through the elimination of dust generated from the transfer robot, that is, mechanical contamination, by supplying and exhausting an inert gas to and from the vacuum process chamber and the transfer chamber (excluding the entry and exit chambers) during substrate transfer. Since the inert gas is supplied and exhausted to and from the transfer chamber and vacuum process chamber (excluding the entry and exit chambers), it is believed to be possible to eliminate the above-mentioned chemical contamination at least in the transfer chamber and vacuum process chamber.
With this known example, however, even though the entry and exit chambers have a vacuum pump, the inert gas is only exhausted, and not supplied, so it is impossible to prevent contamination caused by trace amounts of volatile impurity components coming from chamber structures (such as the shaft seals of a transfer robot or the O-rings used as chamber seals) or the reverse diffusion of oil from a vacuum pump. Therefore, the entry and exit chambers, and in turn the entire semiconductor manufacturing apparatus, cannot be maintained in a clean state, and the contamination of the substrate surface cannot be effectively prevented.
Also, with the known example, the substrates are introduced into the entry and exit chambers directly in single units, rather than with a cassette that holds a plurality of substrates, but when a cassette that holds a plurality of substrates is used, the substrate is always present in the entry and exit chambers, even while the substrate is being transferred to the process chamber or transfer chamber after cassette insertion, so even though the entry and exit chambers are exhausted, the substrate present in the entry and exit chambers can still end up being contaminated by reverse diffusion of oil from the vacuum pump or other such chemical contamination.
In light of the above situation, it is an object of the present invention to provide a semiconductor manufacturing method, a substrate processing method, and a semiconductor manufacturing apparatus with which not only the transfer chamber and the process chamber but the preliminary chamber can be maintained in a clean state, allowing the substrate transfer environment to be adjusted to prevent contamination of the substrate surface by impurities, and affording low cost and easy maintenance.
The semiconductor manufacturing method of the first invention comprises the steps of exchanging a substrate between a preliminary chamber and the outside, subjecting the substrate to a predetermined processing in a process chamber, transferring the substrate through a transfer chamber provided between the preliminary chamber and the process chamber, and supplying and exhausting an inert gas to and from at least the chamber in which the substrate is present among the chambers during the transfer of the substrate. The predetermined processing may be any processing treating a gas in the manufacture of a semiconductor element, such as vapor phase growth. Supplying and exhausting an inert gas to and from at least the chamber in which the substrate is present during the transfer of the substrate allows a predetermined gas flow to be formed within at least the chamber in which the substrate is present, and by maintaining this chamber in a predetermined pressure state and transferring the substrate under this pressure, chemical contamination can be effectively prevented in at least the chambers in which the substrate is present, and contamination of the substrate surface during its transfer can be minimized.
The semiconductor manufacturing method of the second invention comprises the steps of exchanging a substrate between a preliminary chamber and the outside, subjecting the substrate to a predetermined processing in a process chamber, transferring the substrate through a transfer chamber provided between the preliminary chamber and the process chamber, and supplying and exhausting an inert gas to and from all of the chambers during the transfer of the substrate. It is preferable for an inert gas to be supplied to and exhausted from all of the chambers because a predetermined gas flow can be formed within all the chambers, chemical contamination can be prevented more effectively, and transfer will be more efficient.
The semiconductor manufacturing method of the third invention comprises the steps of exchanging a substrate between a preliminary chamber and the outside, subjecting the substrate to a predetermined processing in a process chamber, transferring the substrate through a transfer chamber provided between the preliminary chamber and the process chamber, and supplying and exhausting an inert gas to and from at least the chamber equipped with a vacuum pump among the chamber during the transfer of the substrate. Since an inert gas is supplied to and exhausted from at least the chamber equipped with a vacuum pump during the transfer of the substrate, and a gas flow is formed, reverse diffusion of oil from the vacuum pump can be effectively prevented.
In the first invention above, it is preferable for the exchange of the substrate between the preliminary chamber and the outside to be carried out with a cassette that holds a plurality of substrates. If a cassette that holds a plurality of substrates, rather than a single substrate, is transferred into the preliminary chamber, then after this cassette transfer a substrate will be present in the preliminary chamber even during substrate transfer, so when preventing chemical contamination is taken into account, inert gas must be supplied and exhausted to and from the preliminary chamber at all times. In this respect, with the present invention inert gas is supplied to and exhausted from the preliminary chamber, which is one of the chambers in which a substrate is present, so contamination of the substrate surface present at all times in the preliminary chamber can be minimized.
Also, in the first invention, it is preferable for the predetermined processing to which the substrate is subjected in the process chamber to be HSG formation or epitaxial growth. In an HSG formation process, the pressure inside the chamber which should be maintained is higher than in the past, with at least 50 Pa being preferable, for example, in an epitaxial growth process, it is preferable for the pressure inside the chamber which should be maintained is about 400 to 1333 Pa, for example. With an HSG formation process, contamination by gaseous particles results in non-uniform dangling bond density of the silicon molecules, and with an epitaxial growth process, the presence of chemical contaminants causes mismatching in the crystallinity of the silicon, resulting in crystal defects or polycrystallization, and this has an adverse effect on the quality of the finished product, but with the present invention, this effect can be reduced because an inert gas is supplied to and exhausted from the chamber in which the substrate is present. With a process in which a film thickness is made smaller such as a formation process of a gate oxide film or the like, a proportion for which one molecule of contaminant accounts on the total film thickness becomes large, so the effect on the film thickness uniformity and the characteristics of the device cannot be ignored, but here again, this effect can be reduced with the present invention.
The substrate processing method of the fourth invention comprises the steps of exchanging a substrate between a preliminary chamber and the outside, subjecting the substrate to a predetermined processing in a process chamber, transferring the substrate through a transfer chamber provided between the preliminary chamber and the process chamber, and supplying and exhausting an inert gas to and from at least the chamber in which the substrate is present among the chambers during the transfer of the substrate. The substrate may be a glass substrate, as well as a semiconductor substrate. The predetermined processing may be any processing treating a gas in the processing of the substrate, such as a process of vapor phase growth. Since an inert gas is supplied to and exhausted from at least the chamber in which the substrate is present during the transfer of the substrate, chemical contamination can be effectively prevented in at least the chamber in which the substrate is present, and contamination of the substrate surface during transfer can be minimized.
The semiconductor manufacturing apparatus of the fifth invention comprises a preliminary chamber from and to which a substrate is exchanged with the outside, a process chamber in which the substrate is subjected to a predetermined processing, a transfer chamber in which the substrate is transferred between the preliminary chamber and the process chamber by a built-in transfer robot, inert gas supply portion provided to each of the chambers that supplies an inert gas into the corresponding chamber, gas exhaust portion provided to each of chambers that exhausts the gas from the corresponding chamber, and controller that controls the inert gas supply portion and gas exhaust portion and thereby supplying and exhausting an inert gas to and from at least the chamber in which the substrate is present during the transfer of the substrate. The predetermined processing may be any processing treating a gas in the manufacture of a semiconductor element, such as a process of vapor phase growth. Chemical contamination can be effectively prevented in at least the chamber in which the substrate is present, and contamination of the substrate surface during transfer can be minimized with a simple structure merely entailing the provision of controller that supplies and exhausts an inert gas to and from at least the chamber in which the substrate is present during the transfer of the substrate.
In the fifth invention above, it is preferable for the preliminary chamber to be a cassette chamber into which is transferred a cassette that holds a plurality of substrates. If the preliminary chamber is a cassette chamber into which is transferred a cassette that holds a plurality of substrates, rather than a single substrates then after this cassette transfer a substrate will be present in the preliminary chamber even during substrate transfer, so when preventing chemical contamination is taken into account, inert gas must be supplied and exhausted to and from the preliminary chamber at all times in this respect, with the present invention inert gas is supplied to and exhausted from the preliminary chamber, which is one of the chambers in which a substrate is present, so contamination of the substrate surface present at all times in the preliminary chamber can be minimized.